[cDAC] ISOSDacInterface::GetSyncBlockData #119320
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| # Contract Object | ||
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| This contract is for getting information about SyncBlocks. | ||
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| ## APIs of contract | ||
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| ```csharp | ||
| public readonly struct SyncBlockData | ||
| { | ||
| public bool IsFree { get; init; } | ||
| public TargetPointer SyncBlock { get; init; } | ||
| public TargetPointer Object { get; init; } | ||
| public uint RecursionLevel { get; init; } | ||
| public uint HoldingThreadId { get; init; } | ||
| public uint MonitorHeldState { get; init; } | ||
| } | ||
| ``` | ||
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| ``` csharp | ||
| // Get the number of syncblocks that have ever been used in the target runtime. | ||
| uint GetSyncBlockCount(); | ||
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| // Get information about a syncblock at a given index. | ||
| SyncBlockData GetSyncBlockData(uint index); | ||
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| // Get the number of threads waiting on the syncblock at a given index (up to the maximumIteration). | ||
| uint GetAdditionalThreadCount(uint index, uint maximumIterations = 1000); | ||
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| // Get built-in COM data for the syncblock if available. Returns false if the syncblock at the given index does not have COM data. | ||
| bool TryGetBuiltInComData(uint index, out TargetPointer rcw, out TargetPointer ccw, out TargetPointer cf); | ||
| ``` | ||
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| ## Version 1 | ||
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| Data descriptors used: | ||
| | Data Descriptor Name | Field | Meaning | | ||
| | --- | --- | --- | | ||
| | `InteropSyncBlockInfo` | `ClassFactory` | Pointer to the ClassFactory for the object (if it exists) | | ||
| | `InteropSyncBlockInfo` | `RCW` | Pointer to the RCW for the object (if it exists) | | ||
| | `InteropSyncBlockInfo` | `CCW` | Pointer to the CCW for the object (if it exists) | | ||
| | `SyncBlock` | `Monitor` | `AwareLock` storing the `SyncBlock`s locking state | | ||
| | `SyncBlock` | `InteropInfo` | Pointer to an optional `InteropSyncBlockInfo` for the sync block | | ||
| | `SyncBlock` | `Link` | `SLink` to list of threads waiting on the `SyncBlock` | | ||
| | `SyncTableEntry` | `SyncBlock` | `SyncBlock` corresponding to the entry | | ||
| | `SyncTableEntry` | `Object` | `Object` corresponding to the entry | | ||
| | `SyncBlockCache` | `FreeSyncTableIndex` | Pointer to the first syncblock index which has never been used in the target runtime | | ||
| | `AwareLock` | `RecursionLevel` | RecursionLevel of the `AwareLock` | | ||
| | `AwareLock` | `HoldingThreadId` | ThreadId currently holding the `AwareLock` | | ||
| | `AwareLock` | `LockState` | `uint` flag mask containing lock state information | | ||
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| Global variables used: | ||
| | Global Name | Type | Purpose | | ||
| | --- | --- | --- | | ||
| | `SyncTableEntries` | TargetPointer | The `SyncTableEntry` list | | ||
| | `SyncBlockCache` | TargetPointer | The global `SyncBlockCache` | | ||
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| Constants used: | ||
| | Name | Type | Purpose | Value | | ||
| | --- | --- | --- | --- | | ||
| | `WAITER_COUNT_SHIFT` | uint | AwareLock LockState shift to get waiter count | `0x6` | | ||
| | `IS_LOCKED_MASK` | uint | AwareLock LockState mask to determine if locked | `0x1` | | ||
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| Contracts used: | ||
| | Contract Name | | ||
| | --- | | ||
| | _(none)_ | | ||
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| ``` csharp | ||
| uint GetSyncBlockCount() | ||
| { | ||
| TargetPointer syncBlockCacheAddr = target.ReadPointer(target.ReadGlobalPointer("SyncBlockCache")); | ||
| uint freeSyncTableIndex = target.Read<uint>(syncBlockCacheAddr + /* SyncBlockCache::FreeSyncTableIndex offset */); | ||
| // freeSyncTableIndex points to the first unused SyncBlock | ||
| return freeSyncTableIndex - 1; | ||
| } | ||
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| SyncBlockData GetSyncBlockData(uint index) | ||
| { | ||
| TargetPointer syncTableEntry = target.ReadPointer(GetSyncTableEntryAddress(index)); | ||
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| TargetPointer pObject = target.ReadPointer(syncTableEntry + /* SyncTableEntry::Object offset */); | ||
| TargetPointer pSyncBlock = target.ReadPointer(syncTableEntry + /* SyncTableEntry::SyncBlock offset */); | ||
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| // SyncBlock is free if lowest bit of the Object field is set. | ||
| if ((pObject & 0x1) == 0x1) | ||
| return new SyncBlockData { IsFree = true }; | ||
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| if (pSyncBlock != TargetPointer.Null) | ||
| { | ||
| TargetPointer pMonitor = target.ReadPointer(pSyncBlock + /* SyncBlock::Monitor offset */); | ||
| uint lockState = target.Read<uint>(pMonitor + /* AwareLock::LockState offset */) | ||
| bool locked = (lockState & IS_LOCKED_MASK) == IS_LOCKED_MASK; | ||
| uint waiterCount = lockState >> WAITER_COUNT_SHIFT; | ||
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| // monitorHeldState lsb is 1 if locked, 0 if unlocked | ||
| // the higher bits contain the waiter count shifted up | ||
| uint monitorHeldState = (locked ? 0x1 : 0x0) | (waiterCount << 1); | ||
| return new SyncBlockData | ||
| { | ||
| IsFree = false, | ||
| Object = pObject, | ||
| SyncBlock = pSyncBlock, | ||
| RecursionLevel = target.Read<uint>(pMonitor + /* AwareLock::RecursionLevel offset */), | ||
| HoldingThreadId = target.Read<uint>(pMonitor + /* AwareLock::HoldingThreadId offset */), | ||
| MonitorHeldState = monitorHeldState, | ||
| }; | ||
| } | ||
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| return new SyncBlockData | ||
| { | ||
| IsFree = false, | ||
| Object = pObject, | ||
| SyncBlock = pSyncBlock, | ||
| RecursionLevel = 0, | ||
| HoldingThreadId = 0, | ||
| MonitorHeldState = 0 | ||
| }; | ||
| } | ||
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| uint GetAdditionalThreadCount(uint index, uint maximumIterations) | ||
| { | ||
| TargetPointer syncTableEntry = target.ReadPointer(GetSyncTableEntryAddress(index)); | ||
| TargetPointer syncBlock = target.ReadPointer(syncTableEntry + /* SyncTableEntry::SyncBlock offset */); | ||
| if (syncBlock == TargetPointer.Null) | ||
| return 0; | ||
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| uint additionalThreadCount = 0; | ||
| TargetPointer pLink = target.ReadPointer(syncBlock + /* SyncBlock::Link offset */); | ||
| while (pLink != TargetPointer.Null && additionalThreadCount < maximumIterations) | ||
| { | ||
| additionalThreadCount += 1; | ||
| pLink = target.ReadPointer(pLink); | ||
| } | ||
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| return additionalThreadCount; | ||
| } | ||
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| bool GetBuiltInComData(uint index, out TargetPointer rcw, out TargetPointer ccw, out TargetPointer cf); | ||
| { | ||
| TargetPointer syncTableEntry = target.ReadPointer(GetSyncTableEntryAddress(index)); | ||
| TargetPointer syncBlock = target.ReadPointer(syncTableEntry + /* SyncTableEntry::SyncBlock offset */); | ||
| if (syncBlock == TargetPointer.Null) | ||
| return false; | ||
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| TargetPointer interopInfo = target.ReadPointer(syncBlock + /* SyncBlock::InteropInfo offset */); | ||
| if (interopInfo == TargetPointer.Null) | ||
| return false; | ||
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| rcw = target.ReadPointer(interopInfo + /* InteropSyncBlockInfo::RCW offset */); | ||
| ccw = target.ReadPointer(interopInfo + /* InteropSyncBlockInfo::CCW offset */); | ||
| cf = target.ReadPointer(interopInfo + /* InteropSyncBlockInfo::ClassFactory offset */); | ||
| return rcw != TargetPointer.Null || ccw != TargetPointer.Null || cf != TargetPointer.Null; | ||
| } | ||
| ``` | ||
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| Helpers: | ||
| ```csharp | ||
| private TargetPointer GetSyncTableEntryAddress(uint index) | ||
| { | ||
| TargetPointer syncTableEntries = target.ReadPointer(target.ReadGlobalPointer("SyncTableEntries")); | ||
| uint syncTableEntrySize = target.GetTypeInfo(DataType.SyncTableEntry).Size; | ||
| return syncTableEntries + (syncTableEntrySize * index) | ||
| } | ||
| ``` | ||
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| Original file line number | Diff line number | Diff line change |
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@@ -24,5 +24,6 @@ | |
| "RuntimeTypeSystem": 1, | ||
| "StackWalk": 1, | ||
| "StressLog": 2, | ||
| "SyncBlock": 1, | ||
| "Thread": 1 | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,32 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| using System; | ||
| using System.Diagnostics.CodeAnalysis; | ||
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| namespace Microsoft.Diagnostics.DataContractReader.Contracts; | ||
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| public readonly struct SyncBlockData | ||
| { | ||
| public bool IsFree { get; init; } | ||
| public TargetPointer SyncBlock { get; init; } | ||
| public TargetPointer Object { get; init; } | ||
| public uint RecursionLevel { get; init; } | ||
| public uint HoldingThreadId { get; init; } | ||
| public uint MonitorHeldState { get; init; } | ||
| } | ||
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| public interface ISyncBlock : IContract | ||
| { | ||
| static string IContract.Name { get; } = nameof(SyncBlock); | ||
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| uint GetSyncBlockCount() => throw new NotImplementedException(); | ||
| SyncBlockData GetSyncBlockData(uint index) => throw new NotImplementedException(); | ||
| uint GetAdditionalThreadCount(uint index, uint maximumIterations = 1000) => throw new NotImplementedException(); | ||
| bool TryGetBuiltInComData(uint index, out TargetPointer rcw, out TargetPointer ccw, out TargetPointer cf) => throw new NotImplementedException(); | ||
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Member
There was a problem hiding this comment. I think we should reconsider this. This approach is coupling COM and the sync block, which is an implementation detail I would avoid. Can we instead place this on the object and abstract away the sync block?
Member
Author
There was a problem hiding this comment. Discussed with Jeremy, we will plan to make a new To get the CCW/RCW of an Object, the public bool GetObjectRCW(TargetPointer objectAddress)
{
IObject object = _target.Contracts.Object;
ISyncBlock sync = _target.Contracts.SyncBlock;
uint syncBlockIndex = object.GetSyncBlockIndex(objectAddress);
TargetPointer interopSyncBlockAddress = sync.GetInteropData(syncBlockIndex);
Data.InteropSyncBlockInfo interopInfo = _target.ProcessedData.GetOrAdd<Data.InteropSyncBlock>(interopSyncBlockAddress);
return interopInfo.rcw;
} |
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| } | ||
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| public readonly struct SyncBlock : ISyncBlock | ||
| { | ||
| // Everything throws NotImplementedException | ||
| } | ||
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I think we should hold off on this for a bit. @jkoritzinsky is reworking the monitors and how they exist on the sync block. See #118371.